Flash suppression is what happens when you see a bright light like a camera flash or a lightning bolt and then suddenly can't see anything for a little bit afterwards. This happens because your eyes have special cells called rods and cones that help you see. When there's a very bright light like a flash, the cells get overwhelmed and stop sending signals to your brain for a little while. This is kind of like when you put your hands over your ears when someone yells really loudly - you can't hear anything for a bit afterwards.
But don't worry, your eyes will start working again after a few seconds and you'll be able to see normally! In fact, your eyes are pretty amazing because they're able to adjust to different levels of light really quickly. So next time you see a bright flash, just give your eyes a few seconds to recover and you'll be good to go!